The existence of dark matter is an ancient mystery in our universe. Dark matter makes up a quarter of our universe, but it doesn’t interact much with ordinary matter. The existence of dark matter has been confirmed by a series of astrophysical and cosmological observations, including stunning images recently taken by the James Webb Space Telescope. However, no experimental observations of dark matter have been reported to date. The existence of dark matter has been a question that astrophysicists around the world have been investigating for decades.

“This is why we do research in fundamental science, exploring the deepest secrets of the universe. The Large Hadron Collider at CERN is the largest experiment ever built, and the collisions of particles that create Big Bang-like conditions can be used to look for clues of dark matter.” says Professor Deepak Kar from CERN University’s Faculty of Physics. Witwatersrand, Johannesburg, South Africa.

Carr, who worked on the ATLAS experiment at CERN, and his former Ph.D. Student Sukanya Sinha (now a PhD student at the University of Manchester) has pioneered a new way to investigate dark matter. Their research was published in the journal Physics Letters B.

“Over the past few decades, there have been many searches for dark matter at the collider, focusing on weakly interacting massive particles called WIMPs,” says Carr. “WIMPS are a class of particles that have been proposed to explain dark matter because they do not absorb or emit light and do not interact strongly with other particles. But since no evidence of WIMPS has yet been found, we realized that the search for dark matter required a paradigm shift.”

“We wondered whether dark matter particles actually form within a jet of Standard Model particles,” Carr said. This led to the search for new detectors known as semi-visible jets that scientists had previously overlooked.

The collision of high-energy protons often results in a collimated spray of particles that gather in what are called jets, a result of the decay of ordinary quarks or gluons. Semi-visible jets would arise when hypothetical dark quarks decay partly into Standard Model quarks (known particles) and partly into stable dark hadrons (“invisible particle”).

Since they are produced in pairs, usually with additional standard model nozzles, if all nozzles are not fully balanced, energy imbalance or lack of energy in the detector will occur. The direction of the lost energy is usually aligned with one of the semi-visible jets.

This makes searching for semi-visible jets very difficult, as this event signature can also result from mismeasured jets at the detector. Kar and Sinha’s new method for searching for dark matter opens new directions in the search for dark matter.

“Although my doctoral thesis does not involve the discovery of dark matter, it establishes the first and fairly tight upper limits for this production method and is already inspiring further research,” says Sinha.